Nuclear Stellar Properties of Swift-BAT AGN and Matched Inactive Galaxies
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MNRAS 473, 4582–4611 (2018) doi:10.1093/mnras/stx2618 Advance Access publication 2017 October 9 LLAMA: nuclear stellar properties of Swift-BAT AGN and matched inactive galaxies Ming-Yi Lin,1‹ R. I. Davies,1‹ E. K. S. Hicks,2 L. Burtscher,1 A. Contursi,1 R. Genzel,1 M. Koss,3 D. Lutz,1 W. Maciejewski,4 F. Muller-S¨ anchez,´ 5 G. Orban de Xivry,6 C. Ricci,7 R. Riffel,8 R. A. Riffel,9 D. Rosario,10 M. Schartmann,1,11,12 A. Schnorr-Muller,¨ 8 T. Shimizu,1 A. Sternberg,13 E. Sturm,1 T. Storchi-Bergmann,8 L. Tacconi1 and S. Veilleux14 1Max–Planck–Institut fur¨ extraterrestrische Physik, Postfach 1312, D-85741 Garching, Germany 2Department of Physics and Astronomy, University of Alaska Anchorage, AK 99508-4664, USA 3Institute for Astronomy, Department of Physics, ETH Zurich, Wolfgang–Pauli–Strasse 27, CH-8093 Zurich, Switzerland 4Astrophysics Research Institute, Liverpool John Moores University, IC2 Liverpool Science Park, 146 Brownlow Hill, L3 5RF, UK 5Center for Astrophysics and Space Astronomy, University of Colorado, Boulder, CO 80309-0389, USA 6Space Sciences, Technologies, and Astrophysics Research Institute, UniversitedeLi´ ege,` 4000 Sart Tilman, Belgium 7Instituto de Astrof´ısica, Facultad de F´ısica, Pontificia Universidad Catolica´ de Chile, Casilla 306, Santiago 22, Chile 8Departamento de Astronomia, Universidade Federal do Rio Grande do Sul, IF, CP 15051, 91501-970 Porto Alegre, RS, Brazil 9Departamento de F´ısica, Centro de Cienciasˆ Naturais e Exatas, Universidade Federal de Santa Maria, 97105-900 Santa Maria, RS, Brazil 10Department of Physics, Durham University, South Road, Durham, DH1 3LE, UK 11Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Hawthorn, Victoria 3122, Australia 12Universitats–Sternwarte¨ Munchen,¨ Scheinerstrasse 1, D-81679 Munchen,¨ Germany 13Raymond and Beverly Sackler School of Physics and Astronomy, Tel Aviv University, Ramat Aviv 69978, Israel 14Department of Astronomy and Joint Space–Science Institute, University of Maryland, College Park, MD 20742-2421, USA Accepted 2017 October 5. Received 2017 October 5; in original form 2017 June 10 ABSTRACT In a complete sample of local 14–195 keV selected active galactic nuclei (AGNs) and inactive galaxies, matched by their host galaxy properties, we study the spatially resolved stellar kinematics and luminosity distributions at near-infrared wavelengths on scales of 10–150 pc, using SINFONI on the VLT. In this paper, we present the first half of the sample, which comprises 13 galaxies, eight AGNs and five inactive galaxies. The stellar velocity fields show a disc-like rotating pattern, for which the kinematic position angle is in agreement with the photometric position angle obtained from large scale images. For this set of galaxies, the stellar surface brightness of the inactive galaxy sample is generally comparable to the matched sample of AGN, but extends to lower surface brightness. After removal of the bulge contribution, we find a nuclear stellar light excess with an extended nuclear disc structure, which exhibits a size-luminosity relation. While we expect the excess luminosity to be associated with a dynamically cooler young stellar population, we do not typically see a matching drop in dispersion. This may be because these galaxies have pseudo-bulges in which the intrinsic dispersion increases towards the centre. And although the young stars may have an impact in the observed kinematics, their fraction is too small to dominate over the bulge and compensate the increase in dispersion at small radii, so no dispersion drop is seen. Finally, we find no evidence for a difference in the stellar kinematics and nuclear stellar luminosity excess between these active and inactive galaxies. Key words: galaxies: kinematics and dynamics – galaxies: photometry – galaxies: Seyfert – galaxies: spiral. E-mail: [email protected], [email protected] (M-yL); davies@ mpe.mpg.de (RID) C 2017 The Authors Downloaded from https://academic.oup.com/mnras/article-abstract/473/4/4582/4411840Published by Oxford University Press on behalf of the Royal Astronomical Society by Universidade Federal do Rio Grande do Sul user on 08 March 2018 Nuclear stellar properties in LLAMA galaxies 4583 with XSHOOTER. This is the LLAMA (Luminous Local AGN 1 INTRODUCTION with Matched Analogues) survey, which has been the focus of sev- It is widely accepted that most galaxies harbour a supermassive eral other studies (Schnorr-Muller¨ et al. 2016; Davies et al. 2017, black hole (SMBH). The most remarkable BH observations are Rosario et al. submitted, Burtscher et al. in preparation). of the Galactic Centre where the individual stars can be spa- In this paper, we present the SINFONI H+K observations prob- tially resolved and followed through their orbits, accurately con- ing radial scales of ∼150 parsec for the first half of the AGNs straining the SMBH mass (for a review see Genzel, Eisenhauer from Davies et al. (2015) and their corresponding inactive galaxies & Gillessen 2010). Beyond the Milky Way, the most compelling which are matched in stellar mass, morphology, inclination and the evidence is the correlation between the mass of SMBH and stel- presence of a bar. This contains a total of 13 galaxies, eight AGNs lar velocity dispersion of the bulge component of the host galaxy, and five inactive galaxies, which provide eight pairs (since some which is interpreted as the signature of coevolution and regulation inactive galaxies can be well matched to more than one AGN). In between the SMBH and the bulge (see Kormendy & Ho 2013 and this study, because the sample number is small, when comparing the reference therein). The SMBH grows via inflowing gas accre- a difference between active and inactive sample for any physical tion, resulting in active galactic nuclei (AGN), which have been quantity, we directly compare the mean value and standard devia- observed across different cosmic times. The host galaxy growth tion rather than giving a statistical test. In Section 2, we introduce typically follows two plausible modes (Shlosman 2013): (i) galaxy the observations and data reduction of all the galaxies. Section 3 merger: angular momentum dissipation leads the gas infall forming describes the methodology to extract the stellar kinematics and con- compact young stars in the host galaxy (Holtzman et al. 1992; strain the bulge Sersic´ parameters. The nuclear stellar photometry Hopkins et al. 2009), and furthermore efficiently drives some is in Section 4, while the nuclear stellar kinematics is presented in amount of gas to feed the central SMBH. Examples of this in- Section 5. We summarize our conclusions in Section 6. Throughout clude the ultraluminous infrared bright galaxies with disturbed host this paper, we focus the discussion on the overall kinematic and pho- galaxy morphologies, which are usually accompanied by a QSO- tometric properties of the active and inactive samples. A detailed like luminous AGN (Bennert et al. 2008; Veilleux et al. 2009;Teng descriptions of individual objects with special (or extreme) proper- & Veilleux 2010; Ricci et al. 2017). (ii) Secular process of cold ties will be discussed throughout this paper. We assume a standard −1 −1 gas inflow: gas transfers from outer host galaxy to inner circum- cold dark matter (CDM) model with H0 = 73 km s Mpc , nuclear regions through disc and bar instabilities. If a bar drives = 0.73 and M = 0.27. the gas inflow, the associated inner Lindblad resonance (ILR) may terminate the inflowing gas and redistribute it in a disc inside the ILR radius (see Combes 2001 and references therein). However, 2 SAMPLE SELECTION, OBSERVATIONS Haan et al. (2009) studied gravitational torques and concluded that AND DATA REDUCTION such dynamical barriers can be easily overcome by gas flows from other non-axisymmetric structures. The direct observations of in- 2.1 Matched Seyfert and inactive galaxy sample ∼ flows in an ionized or warm molecular gas phase on 100 pc scales The sample is drawn from the LLAMA project, the selection details have been confirmed in nearby Seyferts (e.g. Storchi-Bergmann and the scientific rationale for which have been described in Davies et al. 2007;Muller¨ Sanchez´ et al. 2009; Riffel, Storchi-Bergmann & et al. (2015). We briefly address and discuss the key aspects of our Winge 2013;Daviesetal.2014; Storchi-Bergmann 2014; Schnorr- target strategy below. Muller¨ et al. 2017). The studies above focus on the question of the origin of inflow- (i) Select AGNs from the 58-month Swift-BAT catalogue: ing gas transport (e.g. ex-situ gas). Once the gas accumulates in the The Swift Burst Alert Telescope (BAT) all-sky hard X-ray sur- nuclear regions, we further want to know whether any in situ star vey is a robust tool for selecting an AGN, because it is based on formation occurs. Some observations indicate on-going star forma- observations in the 14–195 keV band. Emission in this band is gen- tion in the nuclear region (Riffel et al. 2009;Esquejetal.2014) while erated close to the SMBH and can penetrate through foreground others point out the galaxies prefer to have post-starburst popula- obscuration. In contrast to optical/near-infrared AGN classification tions (Cid Fernandes et al. 2004; Davies 2007;Sanietal.2012;Lin techniques, hard X-ray surveys suffer little contamination from non- et al. 2016). Hicks et al. (2013) also find no evidence that on-going nuclear emission. However, it is still biased against extremely ob- 25 −2 star formation is happening in the central 100 pc. Observationally, scured Compton-thick sources (NH ≥ 10 cm , Ricci et al. 2015; it is unclear whether nuclear star formation plays a decisive role in Koss et al. 2016) where the hard X-ray photon attenuation is due triggering nuclear activity. While it is understood that AGN flicker to Compton scattering on electrons rather than photoelectric ab- on and off on very rapid time-scales, a recent analysis points to 105 sorption.